98 Expedition multiple problems

So I picked up a 98 Expedition Eddie Bauer for cheap thinking it needed a fuel pump. It had no fuel pressure. It cranks and cranks but never fires.

I replaced the fuel pump but before I put it back in the tank, I decided to test it on the car. This is when I started noticing bad stuff.

The fuel pump does not kick on. I tested the wires with a test light and it's not getting power. The fuse is good. Have not checked the relay.

- No power to fuel pump
- All fuses under the hood are hot all the time, even without the key, and a good half of them under the dash are also hot all the time
- Running board lights and interior lights stay on all the time
- Injectors are not firing (tested with fuel injector test nodes) even during cranking
- Scanner will not communicate with the computer, and acts weird

It had a melted/shorted out tach wire for the remote start, which is connected to a coil, which I think may have fried the ECU.

So, I'm leaning toward a bad ECU or could it be something else? Does anti-theft cut fuel? I had a friend check out the key and he said it does have a chip in it, but there's no theft light in the cluster. There's also a key wrapped under the dash for the remote start, so I think it does have the anti-theft.

Could be a bad GEM module?

Does an ECU require programming/flashing if I were to buy a used one?

Want to get on the right track before I go spending more money. The guy I got it from did have it running, but he said with a bad misfire and it would bog out when pressing the gas. It died at the gas station and he gave up on it.

Any input appreciated. Thanks!

It seems that you have a potential money pit and a lot of headaches to come. Consider getting another truck of the same year and just use this one as a parts car.

That's not what I want to hear! lol


Anyways, the fuse for the PCM was blown. Replaced and now the theft light on the dash comes on and the fuel pump kicks on. Going to put the fuel pump and tank back together and come back with an update.

Alright, got everything back together and got it started for about 10 seconds then it died, and now it just cranks again. It's getting fuel pressure. It did misfire while it ran. No codes show up on the scanner, so not sure where to look next.

Check fuel pressure with a gauge, minimum is around 28lbs to run. Ideal is 34+ at idle.

Check for spark on one plug.

stamp11127 said:

Check fuel pressure with a gauge, minimum is around 28lbs to run. Ideal is 34+ at idle.

Check for spark on one plug.

Click to expand...

I won't have access to a gauge for about another week, but the pump is brand new and it squirts out of there like no tomorrow, so I'm pretty sure the pressure is good. Also the fuel filter looks brand new.

I will have to check spark another time, I'm finished for the day.

But I'm pretty sure it's either the PCM or the GEM box, or both. I noticed the headlights turning on and off by themselves today. 2 power windows don't work. Exterior/interior lights stay on all the time. That plus the blown PCM fuse tells me it's something electrical.

So, got it to run today. It does have a mean, intermittent misfire. Give it too much gas and it bogs down and wants to die. Give it just the right amount and it'll rev up.

Also, I let it run for about 10 minutes and no codes popped up, which doesn't help. What's common on these? Can the PCM cause a misfire condition?

Also, what controls the spark? Do these have ignition control modules or is it controlled by the PCM?

Next time you have it running, hold it at the rpm's where the miss is most prevalent then the ecm should log a code.

Alright, so making a lot of progress.

Found a vacuum leak and fixed it.

Found two cylinders not firing. Replaced the coils and she's running a thousand times better but one cylinder still isn't firing. The coil is sparking but still not firing.

So my only two conclusions would be a bad/clogged injector or a fouled plug, correct?

It's been running good so I thought I'd take it for a drive.

I got to the end of the driveway and it died, wouldn't restart. Pulled it back to where it was sitting and it started right up. What the heckkkk!?

So it sat and ran fine for about 20 minutes before I decided to try again, but with my buddy following me with chains. I got a block away and it did the same thing. Died and would not restart. This time I checked spark and fuel and it was getting both, but still would not start. So we pulled it back to where it was sitting and it started right up, again! What the heck!?!?

I don't see anything special about where it's sitting, it's on level ground. It died on level ground the first time at the end of the driveway. It's got 1/4 tank of gas so that shouldn't be an issue either. It's also still not throwing any codes. I am totally baffled on this one.

Look at the problem logically.

In order to run the engine needs 3 things:
1) Air
2) Fuel in the correct amount and time
3) Spark at the correct time and voltage

Take any one of them away and it doesn't run. I haven't turned blue in the face so I feel it is safe to assume that the air part isn't the problem. That leaves fuel and spark.
If you have a code reader that will also save data, chose a parameter such as the crank position sensor (cps) to measure and go for a drive.
If the reader has problems communicating with the pcm during the drive and doesn't lose power on the obd connector, that would give a clue to an issue with power to the pcm or the pcm ground.
If it has trouble capturing data for the cps, then might be a bad cps.

If you have a fuel pressure gauge, leave it connected but not where it will get damaged. Go for another test drive. When it dies the next time, check the fuel pressure. If it is 0 then there is an issue with the fuel system.

You have noted that your location is "US". That really doesn't help that much. The northern states salt roads in the winter which introduces a corrosion problem to the electric side of things. So, are you in a salt state?

stamp11127 said:

Look at the problem logically.

In order to run the engine needs 3 things:
1) Air
2) Fuel in the correct amount and time
3) Spark at the correct time and voltage

Take any one of them away and it doesn't run. I haven't turned blue in the face so I feel it is safe to assume that the air part isn't the problem. That leaves fuel and spark.
If you have a code reader that will also save data, chose a parameter such as the crank position sensor (cps) to measure and go for a drive.
If the reader has problems communicating with the pcm during the drive and doesn't lose power on the obd connector, that would give a clue to an issue with power to the pcm or the pcm ground.
If it has trouble capturing data for the cps, then might be a bad cps.

If you have a fuel pressure gauge, leave it connected but not where it will get damaged. Go for another test drive. When it dies the next time, check the fuel pressure. If it is 0 then there is an issue with the fuel system.

You have noted that your location is "US". That really doesn't help that much. The northern states salt roads in the winter which introduces a corrosion problem to the electric side of things. So, are you in a salt state?

Click to expand...

Yes, I'm in a salt state.

I checked fuel and it had tons of pressure.

I checked spark and it shocked me... so I assume it had spark.

Does the CPS control the injectors as well?

The code reader is a just a basic reader so I can't read any data.

And it was raining today... I've read alot about these windshields leaking on the GEM module, but would that kill the engine?? Maybe that would explain why it runs fine in a certain spot but won't drive??

EDIT: It doesn't lose power when it dies, just the engine dies, does that rule out the GEM module?

I just read that the CPS would cause a no-start condition if they go bad, but could it be intermittent? Or once they're done, they're done?

I forgot to list the parts replaced by the previous owner:

New vacuum lines (although I still found a leak and fixed one)
All new spark plugs
New EGR Valve
New fuel filter

I've replaced:
Two coils
Fuel pump


Also, it's hard to start and doesn't want to stay running when the engine is cold.

New thread started here:
http://www.expeditionforum.com/f42/some-issues-29399/

This thread is closed.